Integrated circuits, typically based on a silicon wafer, can be mounted on a printed circuit board along with other components, either active or passive. For example, it is known mount active and passive circuits on a printed circuit board as shown in FIG. 1, where the active sides face up and leads are taken down to the PCB.
An alternative solution is shown in FIG. 2 where the components are surface mounted on the PCB using so-called flip-chip technology. Here after fabrication, the integrated circuit (Chip) is flipped over and the active surface bonded to the PCB using solder balls pre-positioned on the contact pads.
Yet, another solution is shown in FIG. 3, where one chip, a passive circuit in this example, is mounted on top of an active circuit. The passive circuit is flip-chipped and surface-mounted on the underlying active circuit using solder balls. The top of the passive circuit is connected to the PCB by leads that are taken down to the PCB. Through-silicon-vias (TSVs) are formed through the passive circuit to connect it directly to corresponding locations on the active circuit.
The advantage of this arrangement is that it substantially reduces the footprint of the device. However, there are many discrete components, such as quartz crystals, surface acoustic wave filters, or other components that still need to be mounted on the PCB, thus substantially contributing to the overall footprint of the device.
US patent publication no. 2011/0045636 describes a method of stacking identical chips using through-silicon vias. However, this method does not eliminate the need to mount additional components as described above on the PCB.